Extracorporeal blood pumps have hitherto been used during or after surgery (see; for example, Patent Document 1). The blood pump is used as an artificial heart and enables midterm assistance of a cardiac function and treatment of the heart. The blood pump is for circulating blood by centrifugal force, and the centrifugal force is acquired by rotation of an impeller accommodated in a housing. A driven magnet is attached to the impeller accommodated in the housing of the blood pump. The impeller is rotated by rotating a drive magnet disposed outside the housing. In the blood pump disclosed in Patent Document 1, magnets are placed in such a way that magnetic coupling occurs in a direction perpendicular to a ground plane. A bearing is set in a flow path running through a bottom of the housing. The blood pump of Patent Document 1 therefore has contact between the impeller and an interior wall of the housing.
A blood pump described in Patent Document 2 is structured such that an impeller is rotated by magnetic coupling between a drive magnet placed around a rotary shaft and a driven magnet placed on an inner periphery of the impeller. The blood pump of Patent Document 2 additionally has a pair of interacting magnets, one on a housing and the other on an outer periphery of the impeller. The pair of magnets operates to magnetically levitate the impeller and prevent contact between the impeller and the housing.
A blood pump described in Patent Document 3 has a magnet on a sidewall of a housing and another magnet on a circumferential periphery of an impeller and is structured to induce magnetic coupling in a radial direction in which an impeller rotates and to rotate the impeller. The blood pump described in Patent Document 3 assures a blood flow path around a rotating shaft. The impeller can be levitated by means of dynamic pressure of blood flowing through the flow path. The flow path formed around the rotating shaft is a triangular bearing hole positioned around the shaft, and the shaft and a portion of the bearing hole remain in contact with each other.